Fig. 2

Fourier spectra of a protein sequence and a single point variant of the same protein. Shown are the Fourier spectra of wild type GLP-1 peptide (in blue) and of its E3A variant (in red). The spectra are obtained after numerically encoding the amino acid sequence using one index from AAindex database and their processing using Fast Fourier Transform (FFT) technique (see Methods section for details). A single point mutation impacts the whole spectrum. In the iSAR methodology, the variations caused by the mutation in the spectra of variants are correlated with variations observed in their corresponding biological activity using the PLS regression technique (see Fig. 3)